Method and apparatus for manufacturing hollow composite magnetic member, and fuel injection valve

Abstract

There is provided a manufacturing method of a hollow composite magnetic member having weakened magnetism in a portion of a ferromagnetic hollow member, the method includes: a step of forming a weak-magnetic area having weakened magnetism by melting and mixing a Ni-containing material and the hollow member by continuously supplying the Ni-containing material to a portion of the hollow member and heating the irradiation area having a line segment shape with the laser beam. Accordingly, since it is possible to prevent drop of a local portion of a hollow ferromagnetic pipe from being easily generated by a weak-magnetization treatment, to greatly reduce deformation generated by laser irradiation, and it becomes unnecessary to adjust the shielding gas pressure inside the pipe, the weak-magnetization treatment can be performed with higher efficiency and higher quality.

The invention claimed is: 
     
       1. A manufacturing method of a hollow composite magnetic member having weakened magnetism in a portion of a ferromagnetic hollow member, the method comprising:
 a step of forming a weak-magnetic area having weakened magnetism by melting and mixing a Ni-containing material and the hollow member by continuously supplying the Ni-containing material to a portion of the hollow member and heating an irradiation area having a line segment shape with a laser beam, wherein
 the Ni-containing material is a single-core solid wire of which cross section is a solid or hollow circular shape, an elliptical shape or a rectangular shape, or a strand wire in which a single-core solid wire of which cross section is a solid or hollow circular shape, an elliptical shape or a rectangular shape is twisted a plurality of times, 
 a length of a short side of the irradiation area is b, 
 a diameter of the cross section of the Ni-containing material is d, and 
 a relationship of b/d≤1.0 is satisfied. 
 
 
     
     
       2. The manufacturing method of a hollow composite magnetic member according to  claim 1 ,
 wherein the hollow member is rotated when the irradiation area is heated. 
 
     
     
       3. The manufacturing method of a hollow composite magnetic member according to  claim 1 ,
 wherein in a case where a length of a long side of the irradiation area is a and a width of the weak-magnetic area in the cross section parallel to the long side of the irradiation area is w, a is 1 time or more and less than 2 times w. 
 
     
     
       4. The manufacturing method of a hollow composite magnetic member according to  claim 1 ,
 wherein the laser beam is formed by a cylindrical lens. 
 
     
     
       5. The manufacturing method of a hollow composite magnetic member according to  claim 1 ,
 wherein the irradiation area having the line segment shape is formed by scanning a laser beam having a point shape. 
 
     
     
       6. The manufacturing method of a hollow composite magnetic member according to  claim 1 , wherein b=0.5 mm and d=0.6 mm.